View of the interior of the Soleil Synchrotron showing the different beamlines including Disco
View of the interior of the Soleil Synchrotron showing the different beamlines including Disco, the beamline that pierced the secret of the Mehrgarh amulet. A beamline serves to extract photons, select their energy range and focus the synchrotron beam on the subject. The Disco microscope, which covers the VUV-visible range from 180 to 1,000 nm, was used to analyse this copper amulet from the Chalcolithic period, discovered at Mehrgarh in present-day Pakistan. This analysis enabled us to work out how it was made. This amulet is the oldest known object made by the lost wax process, which uses a model sculpted in a material like beeswax that is subsequently encased in a clay mould. Because wax melts at low temperature it runs out easily when the clay is heated. Molten metal is then poured into the clay mould, filling the empty space left by the lost wax.